The present invention generally relates to the use of corrosion inhibitor compositions in corrosive environments, such as in subterranean operations, and, more specifically, to corrosion inhibitor compositions comprising organic solvents with a flash point of at least 75° C., and methods of using these compositions in subterranean operations.
The corrosion of metal surfaces occurs when the metal surfaces are contacted by a corrosive environment containing an oxidizer (e.g., an electrochemical oxidizer, a chemical oxidizer or the like). Illustrative corrosive environments include, for example, acidic environments, environments containing water vapor in the presence of air and/or oxygen, and environments containing chloride or bromide ions, carbon dioxide and/or hydrogen sulfide. As used herein, the term “corrosion” refers to any reaction between a material and its environment that causes some deterioration of the material or its properties. Examples of common types of corrosion include, but are not limited to, the rusting of a metal, the dissolution of a metal in acids, and patina development on the surface of a metal.
Acidic environments can be produced by acidic treatment fluids that are commonly used in a number of operations in the oil and gas extractive industries. In such operations, any metal surfaces present are subjected to the corrosive environment of the treatment fluid. For example, metal surfaces (e.g., piping, tubular goods, downhole and surface equipment) can be exposed to acidic treatment fluids in industrial chemical equipment. In subterranean applications, metal surfaces on various types of equipment are often exposed to corrosive conditions during downhole operations. For example, acidic treatment fluids are frequently utilized in the treatment of subterranean formations, and additional corrosive components including brine, carbon dioxide and/or hydrogen sulfide are commonly encountered downhole.
Acidic treatment fluids for downhole use include, for example, acidic clean-up fluids and stimulation fluids. Acidic stimulation fluids include, for example, treatment fluids used in hydraulic fracturing or matrix acidizing treatments. As used herein, the term “treatment fluid” refers to any fluid used in a subterranean application in conjunction with a desired function and/or for a desired purpose. The term “treatment fluid” does not imply any particular action by the fluid or any component thereof. Acidic treatment fluids can include a variety of acids such as, for example, hydrochloric acid, formic acid, hydrofluoric acid, and the like.
While acidic treatment fluids are useful for a variety of downhole operations, they can be somewhat problematic due to potential metal surface corrosion on downhole production tubing and tools, for which the repair or replacement costs are high. Furthermore, under typical downhole conditions, corrosion rates of metal surfaces are frequently increased due to elevated temperatures and pressures that are present in the subterranean environment. In addition to damage caused to downhole metal surfaces, corrosion can result in significant quantities of the acidic treatment fluid containing the corrosion inhibitor composition being introduced into the formation, thereby reducing the treatment fluid's downhole effectiveness at the time of treatment fluid recovery.
To combat potential corrosion problems, various corrosion inhibitors have been used to reduce or substantially prevent corrosion of metal and metal alloy surface on downhole equipment, all with varying levels of success. As used herein, the term “inhibit” and its derivatives refer to a lessening of the tendency of a phenomenon to occur and/or the degree to which that phenomenon occurs. The term “inhibit” does not imply any particular degree or amount of inhibition. Corrosion inhibitor compositions frequently include high vapor pressure organic solvents, specifically methanol, ethanol, n-propanol, or isopropanol, any of which may have health, safety and/or environmental considerations that can geographically limit where they are able to be utilized.